1. Field of the Invention
Image formation devices are known which are used to form fine images. The image formation device includes an electrophotographic photoconductor having a photosensitive layer which is formed on an outer surface of an aluminum drum substrate. To manufacture the aluminum drum substrate, an aluminum ingot is subjected to hot extrusion and cold drawing processes to form a cylindrical tube. The cylindrical tube is then cut to obtain an aluminum raw drum having a predetermined length. Further machining operations are then performed to obtain the aluminum drum substrate having precise dimensions and a specified surface condition. The invention relates to a method of cleaning the aluminum raw drum, after the cold drawing process and cutting of the cylindrical tube to the predetermined length, in the manufacturing process of an aluminum drum substrate.
2. Description of the Related Art
The technology of electrophotography has been developed in the field of copying machines, and recently, has been applied to laser printers and the like. A known image formation device, which forms an image using an electrophotographic process, includes an electrophotographic photoconductor. The electrophotographic photoconductor includes an aluminum drum substrate, and a photosensitive or photoconductive layer, which coats an outer surface of the aluminum drum substrate.
The outer surface and other essential surfaces of the drum substrate have very precise dimensions and specified surface conditions, which are formed in a cutting operation. In the following description, when distinguishing between the aluminum drum substrate before and after finishing to the very precise dimensions and specified surface conditions, the former, that is a drum substrate before the finishing, will be referred to as a raw drum (or an aluminum raw drum).
According to a common method of manufacturing an aluminum raw drum, the raw drum is formed from an aluminum ingot, using the following procedures: melting, adjustment of composition, filtration of insoluble impurities, casting, and homogenizing treatment. The ingot is subjected to a hot extrusion process to form a tube shape, followed by a cold drawing process in which the tube shape is drawn to a specified thickness, to thereby form a cylindrical tube or drum having a specified diameter and thickness. Cutting to a specified length (for example, 240 to 360 mm) and cleaning is then performed.
The above cold drawing process uses drawing oil that exhibits a very high viscosity (kinetic viscosity of 1,000 to 2,000 cSt: centistokes, 1 cSt=10−6 m2/s), for example, polybutylene. The drawing oil causes a large amount of cutting chips, which are created in the cutting step, to adhere to the outer and inner surfaces of the raw drum. Thus, the raw drum must be cleaned to remove the oil and cutting chips. In the conventional cleaning process, which follows the cutting to a specified length, the drawing oil is removed (degreased) using a chlorine-containing organic solvent, such as dichloromethane or trichloroethylene, that exhibits a very high solubility of the drawing oil.
Recently, the restriction of organic solvents, particularly chlorine-containing organic solvents, has been intensified to reduce the adverse effects to the natural environment. As an alternative solvent, using alkali detergents or the like has been proposed. For example, in Japanese Unexamined Patent Application Publication No. 2003-262964, a method of cleaning an aluminum tube for photoconductors has been disclosed, in which degreasing cleaning is performed using alkaline ionic water with a pH value of 10 to 12 at a liquid temperature of 40 to 60° C., while being subjected to ultrasonic vibration. In Japanese Patent No. 3421279, a cleaning method is discussed in which the cutting chips and the cutting oil that adhere to the inner surface of the drum are removed using a jet of high pressure water, and without using a chlorine-containing organic solvent. The water is ejected, at an ejection pressure in a range of 1.47×107 Pa to 1.96×107 Pa, from an ejection nozzle towards the inner surface, while moving the nozzle up and down inside the drum.
The nozzle is moved in a longitudinal direction inside the drum. When only one nozzle is used to treat many raw drums, working time is increased, resulting in poor production. When the number of nozzles used is increased to equal to the number of raw drums, production efficiency is increased, but the equipment becomes complicated. Further, in the case of a large number of nozzles, water consumption becomes a limiting factor, since water flow per nozzle and per unit time is high. Further, when cleaning using a single nozzle, the cleaned portion may become discolored when using certain types of cleaning liquid, due to the increased time required to remove the cutting chips and the drawing oil.
Moreover, if the cutting chips are not completely eliminated, and remain on the inside surface of the raw drum, the cutting chips will be pinched together. Since the inside surface is a reference of centering and is held in the subsequent cutting operation, a center of rotation may be shifted during the cutting, resulting in a deterioration in the concentricity between the inside surface and the outside surface of the worked drum. Accordingly, Japanese (Unexamined Patent Application Publication No. 2003-262964 proposes an additional pre-cleaning process using a shower of tap water before the degreasing step using the alkaline ionic water. However, the tap water shower is insufficient to effectively remove the adhered cutting chips.
Further, the cleaning effect using ultrasonic vibration varies depending on a distance from an ultrasound transducer and on the location condition. For example, if an area to be cleaned is at a back side or in a shadow with reference to the transducer, such as when removing cutting chips from the inner surface of a drum, the cleaning effect is apt to decay and sufficient cleaning is not accomplished.